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Scientists in Hawaii and Texas have unveiled some good news for planned "therapeutic cloning" techniques, in which new genetically-correct tissues would be grown in the lab for transplant into people needing replacement parts.

Quite apart from religious/ethical concerns about the likely need to create human embryos - which would later be discarded - during the cloning process, there have also been practical worries. One of these is that cloned tissue, having been grown using adult somatic cells from the patient, rather than the germ cells normally used to reproduce, might suffer from high rates of mutation.

Adult somatic cells in general show a much higher spontaneous mutation rate than germ cells do, which might support such a theory. This led professor John McCarrey of Texas Uni and his colleagues to test the matter out using Big Blue® proprietary transgenic clone mice. (Nothing to with IBM; supplied by biotech firm Stratagene, in fact).

According to the boffins, cloned mice produced using somatic cells showed no difference in mutation rate compared to naturally conceived germ-cell mice of the same age; the cloning technique didn't, in fact, result in any mutation problem.

McCarrey believes this is due to a "bottleneck" effect resulting from the fact that only one cell is needed to produce a clone.

"Because a random cell population exhibits a low mutation rate overall and only one cell from that population is used for cloning, the likelihood is remote that the cell chosen to be cloned will transfer a genetic mutation to its cloned offspring," says the prof. There's also talk of epigenetic settings in the cell being "reset" during cloning.

This is good news for people in need of some new skin, bone marrow, heart tissue etc., as it eliminates one possible hazard of growing the stuff from their own cells. In the future, it might even be possible to produce entire cloned organs - livers, kidneys etc. - to replace knackered ones. The great advantage of this over using donated parts from someone else - quite apart from the difficulty of finding donors - is that there's no need for a lifelong and quite dangerous drug regime to suppress the body's natural rejection of genetically-different stuff.

The boffins' paper, Epigenetic regulation of genetic integrity is reprogrammed during cloning, was published in the Proceedings of the National Academy of Sciences yesterday. (Abstract here: full article requires subscription.) ®